1. Field of the Invention
The present invention relates generally to methods for fabricating magnetic sensor elements. More particularly, the present invention relates to methods for fabricating dual stripe magnetoresistive (DSMR) sensor elements with enhanced signal amplitudes.
2. Description of the Related Art
The recent and continuing advances in computer and information technology have been made possible not only by the correlating advances in the functionality, reliability and speed of semiconductor integrated circuits, but also by the correlating advances in the storage density and reliability of direct access storage devices (DASDs) employed in digitally encoded magnetic data storage and retrieval.
Storage density of direct access storage devices (DASDs) is typically determined as a real storage density of a magnetic data storage medium formed upon a rotating magnetic data storage disk within a direct access storage device (DASD) magnetic data storage enclosure. The areal storage density of the magnetic data storage medium is defined largely by the track width, the track spacing and the linear magnetic domain density within the magnetic data storage medium. The track width, the track spacing and the linear magnetic domain density within the magnetic data storage medium are in turn determined by several principal factors, including but not limited to: (1) the magnetic read-write characteristics of a magnetic read-write head employed in reading and writing digitally encoded magnetic data from and into the magnetic data storage medium; (2) the magnetic domain characteristics of the magnetic data storage medium; and (3) the separation distance of the magnetic read-write head from the magnetic data storage medium.
With regard to the magnetic read-write characteristics of magnetic read-write heads employed in reading and writing digitally encoded magnetic data from and into a magnetic data storage medium, it is known in the art of magnetic read-write head fabrication that magnetoresistive (MR) sensor elements employed within magnetoresistive (MR) read-write heads are generally superior to other types of magnetic sensor elements when employed in retrieving digitally encoded magnetic data from a magnetic data storage medium. In that regard, magnetoresistive (MR) sensor elements are generally regarded as superior since magnetoresistive (MR) sensor elements are known in the art to provide high output digital read signal amplitudes, with good linear resolution, independent of the relative velocity of a magnetic data storage medium with respect to a magnetoresistive (MR) read-write head having the magnetoresistive (MR) sensor element incorporated therein. Within the general category of magnetoresistive (MR) sensor elements, dual stripe magnetoresistive (DSMR) sensor elements, and in particular longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor elements, are presently of considerable interest insofar as the multiple magnetically biased magnetoresistive (MR) layers employed within longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor elements typically provide enhanced magnetic read signal amplitude and fidelity in comparison with both single stripe magnetoresistive (MR) sensor elements and non-longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor elements.
While longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor elements are thus desirable within the art of digitally encoded magnetic data storage and retrieval, longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor elements are nonetheless not entirely without problems within the art of digitally encoded magnetic data storage and retrieval. In particular, as a data track width within a magnetic medium employed within digitally encoded magnetic data storage and retrieval decreases, it becomes increasingly important that a read track width within a longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor element employed in reading the data within the data track be uniformly magnetically biased. Uniform magnetic bias profiles are desirable within read track widths of longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor elements since such uniform longitudinal magnetic bias profiles provide for optimal magnetic read signal amplitudes within such longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor elements.
It is thus towards the goal of providing, for use within magnetic data storage and retrieval a longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor element with a uniform magnetic bias profile across a read track width of the longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor element that the present invention is most generally directed.
Various methods and resultant magnetic sensor element structures have been disclosed in the art of magnetic sensor element fabrication for forming longitudinal patterned exchange biased magnetic sensor elements with enhanced functionality, enhanced reliability or other desirable properties.
For example, general considerations pertinent to both intrinsic and extrinsic magnetic biasing of magnetoresistive (MR) layers within magnetoresistive (MR) sensor elements, including but not limited to dual stripe magnetoresistive (DSMR) sensor elements, are disclosed within Ashar, Magnetic Disk Drive Technology: Heads, Media, Channel, Interfaces and Integration, IEEE, Inc., New York, 1997, pp. 142-46. Similarly, Schultz, in U.S. Pat. No. 5,666,247, discloses a general method for forming for use within a magnetoresistive (MR) sensor element a magnetoresistive (MR) ferromagnetic layer having an antiferromagnetic layer formed thereupon to provide the magnetoresistive (MR) sensor element with an enhanced magnetic exchange bias of the antiferromagnetic layer with respect to the magnetoresistive (MR) ferromagnetic layer. Within the method, the antiferromagnetic layer is formed at a comparatively low sputter power density in absence of a bias magnetic field, and the antiferromagnetic layer and the underlying magnetoresistive (MR) ferromagnetic layer are then subsequently simultaneously thermally annealed at a comparatively low temperature for a comparatively long time period.
In addition, several disclosures specifically directed towards improved magnetic biasing within soft adjacent layer (SAL) magnetoresistive (MR) sensor elements may also be found within the art of magnetic sensor element fabrication. Included within such disclosures are: (1) Krounbi et al., in U.S. Pat. No. 4,785,366 (a soft adjacent layer (SAL) magnetoresistive sensor element having an antiferromagnetic magnetic biasing layer completely covering a first surface of a soft adjacent layer (SAL) within the soft adjacent layer (SAL) magnetoresistive (MR) sensor element, where the first surface of the soft adjacent layer (SAL) is opposite a second surface of the soft adjacent layer (SAL) which is separated from a track width of a magnetoresistive (MR) layer by a non-magnetic spacer layer); and (2) Chen et al., in U.S. Pat. No. 5,325,253 (a soft adjacent layer (SAL) magnetoresistive (MR) sensor element employing a pair of patterned antiferromagnetic magnetic biasing layers formed upon a pair of opposite ends of a magnetoresistive (MR) layer, a central portion of which magnetoresistive (MR) layer is separated from a soft adjacent layer (SAL) by a non-magnetic spacer layer).
Further, several disclosures which are directed more specifically towards dual stripe magnetoresistive (DSMR) sensor elements, and may include magnetic biasing considerations of such dual stripe magnetoresistive (DSMR) sensor elements, may also be found within the art of magnetoresistive (MR) sensor element fabrication. Included within such disclosures are: (1) Reid, in U.S. Pat. No. 5,079,831 (a dual stripe magnetoresistive (DSMR) sensor element fabricated employing two separate substrates each having one magnetoresistive (MR) layer formed thereupon, where the two separate substrates are subsequently carefully aligned and mated during a process employed for fabricating the dual stripe magnetoresistive (DSMR) sensor element); (2) Smith, in U.S. Pat. No. 5,406,433 (a dual stripe magnetoresistive (DSMR) sensor element where each magnetoresistive (MR) layer is fabricated with a height at least ten times a trackwidth of the dual stripe magnetoresistive (DSMR) sensor element, such that the dual stripe magnetoresistive (DSMR) sensor element may be employed for sensing magnetic signals of increased linear density and decreased track spacing); and (3) Shi et al., in U.S. Pat. No. 5,684,658 (a dual stripe magnetoresistive (DSMR) sensor element where a first trackwidth of a first magnetoresistve (MR) layer is physically offset from a second trackwidth of a second magnetoresistive (MR) layer, to provide in conjunction with an electromagnetic bias direction of the two magnetoresistive (MR) layers variable off-track performance characteristics of the dual stripe magnetoresistive (DSMR) sensor element).
Finally, Gill, in U.S. Pat. No. 5,748,399, discloses a spin valve magnetoresistive (MR) sensor element and a method for fabricating the spin valve magnetoresistive (MR) sensor element, where the spin valve magnetoresistive (MR) sensor element is not catastrophically affected by temperature excursions incident to fabrication or operation of the spin valve magnetoresistive (MR) sensor element. The spin valve magnetoresistive (MR) sensor element realizes this object by fabricating the spin valve magnetoresistive (MR) sensor element with a magnetic biasing such that it is electrically resettable to an initialized operational state after an otherwise catastrophic temperature excursion.
Desirable within the art of longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor element fabrication are additional methods and materials which may be employed for forming longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor elements with enhanced magnetic bias uniformity of the longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor elements within the trackwidths of the longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor elements.
It is towards the foregoing object that the present invention is directed.